Gaseous blasts have been used to attenuate streams of molten material, such as glass or polymers into filaments for many years. One problem with previous blowers, especially those having a very long and narrow outlet, is associated with the need for a uniform velocity profile presented by the moving gas to the molten material to uniformly attenuate the streams into filaments which has been difficult to obtain. The need is especially critical in systems wherein continuous filaments of substantially equal diameters are desired. These problems are greatly magnified when high velocities, for example those approaching sonic velocity, are employed.